It is widely known that electrostatic charges can be frictionally transferred between two dissimilar, nonconductive materials. When this occurs, the electrostatic charge thus created appears at the surfaces of the contacting materials. The magnitude of the generated charge is dependent upon the nature of and, more particularly, the respective conductivity of each material. For example, electrostatic charging occurs when water settles through a hydrocarbon solution. This situation greatly interests the petroleum industry, for when such charges are built up in or around flammable liquids, their eventual discharge can lead to incendiary sparking, and perhaps to a serious fire or explosion.
While incendiary sparking is a problem in the petroleum industry, the potential for fire and explosion is probably at its greatest during product handling, transfer and transportation. For example, static charges are known to accumulate in solvents and fuels when they flow through piping, especially when these liquids flow through high surface area or “fine” filters and other process controls, such as is common during tank truck filling. Countermeasures designed to prevent accumulation of electrostatic charges on a container being filled and to prevent sparks by conducting the container to ground can be employed, such as container grounding (i.e. “earthing”) and bonding. But it has been recognized that these measures are inadequate to deal successfully with all of the electrostatic hazards presented by hydrocarbon fuels.
Alone, grounding and bonding are not sufficient to prevent electrostatic build-up in low conductivity, volatile organic liquids such as distillate fuels like diesel, gasoline, jet fuel, turbine fuels, and kerosene. Similarly, grounding and bonding do not prevent static charge accumulation in relatively clean (i.e., contaminant free) light hydrocarbon oils such as organic solvents and cleaning fluids. This is because the conductivity of these organics is so low that a static charge moves very slowly through these liquids and can take a considerable time to reach the surface of a grounded, conductive container. Until this occurs, a high surface-voltage potential can be achieved, which can create an incendiary spark, thereby causing ignition or explosion.
One can directly attack the source of the increased hazard presented by these low conductivity organic liquids by increasing the conductivity of the liquid with additives. The increased conductivity of the liquid will substantially reduce the time necessary for any charges that exist in the liquid to be conducted away by the grounded inside surface of the container. Various compositions are known for use as additives to increase the electrical conductivity of these liquids.
For example, in the past, halogen-containing additives introduced into fuels have played a significant role in achieving improved conductivity properties in fuels. While these halogen-containing additives are effective as conductivity agents, in certain situations, some halogen-containing hydrocarbon compounds have been linked to human and animal health risks, as well as environmental degradation. Legislative enactments, including the 1990 amendment to “The Clean Air Act” in the United States, signal a trend away from the continued permissible use in media of halogen-containing compounds. Even where the use of halogen-containing additives is still permitted, stringent regulations often govern the use, storage and, in particular, the disposal of and/or treatment of waste streams containing these compositions. Accordingly, a need exists to find fuel additives that improve the conductivity of fuel without posing negative risks to humans, animals, and the environment.